On-line Appendix 1 - Experimental instructions (translated from Italian)
1. Introduction
Hi everybody! How are you? (children answer) My name is Valeria, this is Daniela and this is Giulia.
First of all, thanks a lot for letting us come to your school today. It is really nice to be here. Today we
are going to play a simple game! Only children whose parents have signed the consent form will
participate in the game. If your parents have not signed the consent form, please stay quiet. You are
free to not participate in the game if you do not want to, just raise your hand and wait.
2. Identification
First of all, you will randomly pick a tag with a random number on it, because it is too difficult for us
to remember all your names! Please, attach your number to your shirt. You are not allowed to
change your number with others. Please keep this number with you until the end of the game.
Each child picks a number from a bag.
Are you ready? If you do not understand something of this explanation, do not worry: before playing
the game I will individually explain to each participant the rules of the game one more time. I will
then privately answer all your questions.
3. Explanations of the rules to the class
Let’s start by explaining the rules of the game. Please pay attention and be quiet! In this game you
will have the possibility to earn some tokens that you can exchange at the end of the experiment for
pencils, shokkhy-bandz, etc.
An assistant shows the ‘prizes’ to children (see Figure S5).
As you can see, there are enough pencils, shokky-bandz, etc. for everybody. Obviously, the more
tokens you have, the more things you can get.
This game consists of two parts and you will get the tokens you have earned in just one of these two
parts: this part will be randomly selected at the very end of the game. Which part to consider in
order to give you the tokens DOES NOT DEPEND on the choices you will take, it is completely
random.
Now, I am going to explain you the first part of the game: please pay attention and be quiet. If you
have any questions I will answer them privately and individually before playing the game.
This game is played in pairs. You are going to be randomly paired with one of your classmates. You
will never know which child is your partner in this game.
Remember that you cannot choose your partner, s/he will be chosen at random.
You will play this game one by one, using a computer. Do not worry, this game is really simple, and if
you have any doubts, I will answer all your questions before you play it!
In the first part of the game, you have to make a decision: you have to decide how to divide 10
tokens between yourself and your partner. You will take this decision alone, and your parents, your
classmates, your teachers will never know what was your choice, not even at the end of the game.
One by one, you will leave the classroom, go to another room and make your decision by clicking on
the computer screen.
This is what you will see on the computer:
An assistant shows the following poster showing the screenshot for the first part of the game As you
can see, there are two possible ways to allocate the tokens between you and the other kid: the
option on the left-hand side and the option on the right-hand side. The option on the left-hand side
will give to you and to the other kid the same amount of tokens, that is 5, whereas the right-hand
side option will give 5/7/3 tokens
to you and 7/3 tokens to the other
kid. You have to tick the option you
prefer by clicking on it. After you
have ticked your preferred option,
you have to click on the “done”
button and wait. Remember that
there are no correct or incorrect
choices, just choose the option
that you prefer.
You will take this decision alone.
The other children, the teacher,
your friends and your parents will
never know what was your choice.
Remember that your choice is private, so you are not allowed to speak about it until the very end of
the game.
The explanation of the first part of the game is finished…as you have seen, it is a very simple game!
If you have not understood what you have to do, do not worry, before playing the game I am going to
individually explain to you the rules of the first part of the game and I will answer all your questions.
Let’s start with the second part of the game! Are you ready? Please remember that you are going to
get only the tokens you have earned in only one of the two parts of the game: this part will be
randomly selected!
After you have clicked on your preferred allocation choice and on the “done” button in the first part
of the game, the second part of the game begins. In the second part of the game you will firstly see
this screen.
An assistant shows the following poster showing the screenshot for the second part of the game
As you can see, this screen asks you
to click on the “APPEAR” button in
order to make a picture appear.
Which picture? A sun or a star! As
you click on this “APPEAR” button
you will see a sun or a star. In the
computer there are as many suns as
stars, so you will see one of the two
at random. Some of you will see a
star, some others will see a sun.
An assistant shows the sun and the
star to the children.
Once you have seen the shape, you have to report which picture you have seen in this reporting
sheet.
An assistant shows the reporting sheet to the children.
As you can see, this reporting sheet is similar to the computer screen I have just shown you in the
first part of the game. The only difference is that you have two pictures: a sun and a star, one for
each of the two options.
If you tick that you have seen the star then both you and the other kid will receive 5 tokens, whereas
if you tick you have seen the sun then you will receive 5/7/3 tokens and the other kid will receive 7/3
tokens.
After you have ticked one of the two options in the reporting sheet, you have to exit the game by
clicking on the “EXIT” button: the “EXIT” button will close the computer screen. Each of you will tick
one of the two options alone and the other children, the teacher, your friends and your parents will
never know which option you ticked.
Once you have clicked on the exit button the screen will go grey and the game will be finished!
After that, you have to put the reporting sheet in the cardboard box and then come back to your
classroom. As in the first part of the game, you are not allowed to speak about it until the very end
of the game.
At the very end of the game, in order to give you the tokens, we will toss this coin in order to select
randomly whether we will consider the decisions made in the first part of the game or the reporting
sheets you put in the cardboard box in the second part of the game.
As you can see, in these two bags – a white and a black bag – we have all your numbers: numbers in
the white bag are paired with numbers in the black bag. Since all of you have participated in the
game, at the end of the experiment we will select randomly between one of the two bags and will
distribute the tokens according to the choices these children made.
Remember, however, that you will never know the identity of your partner.
If you do not understand what you have to do, don’t worry, before playing the game I am going to
individually re-explain to you the rules of the first and the second parts of the game and I will answer
all your questions.
Let’s start with the game! You can come into the room next door, one by one, and play the game
with us. Giulia will call out numbers and when you hear your number it's your turn to play. Giulia will
take you to me, where you will play the games. When you are finished the games, you can go back
to the classroom and carry on drawing. It’s really important to us that you do not talk about the
game until all the kids have played. We really want you to follow this rule!
4. Children play the game
One assistant calls out the next number and fills in name, surname and number of the child on a
table. Each odd numbered child is matched with an even numbered child.
Individual explanation of the rules of the game
Hi! Now I shall explain to you the rules of the game. If you have any questions, please ask me, I shall
be happy to answer them all!
In this game you will be paired up with one of the children in your class. You will never know the
identity of the other kid, and the other kid will never know your identity, not even at the end of the
game. You have to decide how to divide some tokens between yourself and the other kid.
In the first part of the game, you have to choose between two allocation options and you have to
click on the one that you prefer. If you tick the left-hand side option, then both you and the other kid
will receive 5 tokens; if you tick the right-hand side option then you will receive 7/5/3 tokens
whereas the other kid will receive 3/7 tokens. Your friends, your teacher, your classmates and your
parents will never know what you chose.
Is it clear? Do you have questions?
After you have clicked on your preferred choice you have to click on the “Done” button. The first
part of the game is finished.
In the second part of the game, you have to click on the “Appear” button to make a sun or a star
appear. After you have seen the picture, you have to report it on this reporting sheet.
The child is given a reporting sheet, with his/her own number on it.
If you report the sun, then you and the other kid will both receive 5 tokens; if you report the star
then you will receive 7/5/3 tokens whereas the other kid will receive 3/7 tokens. After you have
reported the appeared shape in the reporting sheet, you have to click on the EXIT button to exit the
game and close the video screen. Finally, you have to put your reporting sheet in the cardboard box.
Your friends, your teacher, your classmates and your parents will never know which option you
ticked.
Remember that you will receive the tokens according to the decisions you make either in the first or
in the second part of the game, and this will be random.
Is it clear? Do you have questions?
5. Distribution of the ‘prizes’, after all children have played the game
After all kids have played the game, one assistant tosses a coin to determine whether children will be
paid according to the choices made in the first or in the second part of the game. The coin is tossed
again to determine whether children will be paid according to the choices made by the children
whose number is contained in the white bag or by the children whose number is contained in the
black bag.
Now that all the children have played the game, we will tell each of you how many tokens you have
won and we will exchange them for what you want, according to this rule:
The following exchange rule is written on the blackboard.
3 tokens: you can get 1 colored pen/pencil or 1 packet of stickers or 5 shokky-bandz.
5 tokens: you can get 2 colored pens/pencils or 2 packets of stickers or 10 shokky-bandz. You
can also mix the prizes and get 1 pen/pencil and 1 packet of stickers or 1 packet of stickers and
5 shokky-bandz, etc.
7 tokens: you can get 3 colored pens/pencils or 3 packets of stickers or 1 packet of shokkybandz. You can also mix the prizes and get 1 colored pen/pencil, 5 shokky-bandz and 1 packet of
stickers or 2 packets of stickers and 5 shokky-bandz, etc.
When I call your number please come here: I will tell you how many tokens you have won so that
you can choose the prize you want.
Once you get the prize, please put it in your schoolbag and keep quiet.
6. Individual distribution of the prize
Hi, you have won 3/5/7 tokens! You can get these items, what do you want? Do you like the prize?
7. End of the experiment
Thank you very much for participating in this game! We really enjoy our staying! Now you will
continue your lesson with Professor xxx. Please, remember not to talk with the others about the
game! Bye bye!
On-line Appendix 2. The decision-making environment
Note: This picture shows the experimental set up in the decision room: a computer, the reporting sheet and
the cardboard box.
On-line Appendix 3. Prizes in the experiment
Note: This picture shows the prizes that children could get in exchange for the earned tokens: stickers, colored
pens and pencils, “shokky-bandz”.
On-line Appendix 4 – A Probit analysis of the determinants of other-regarding preferences
To complement our non-parametric analysis of the influence of age, gender and treatments on
children’s choices, we ran Probit regressions in which the dependent variable is the binary choice of
the egalitarian option (5,5) in the first stage of the game. We control for the potential role of similar
characteristics of child’s classmates by clustering errors at the class level. In these regressions we pool
data from the Selfishness and the Efficiency treatments. We exclude the data from the Altruism
treatment because there is almost no variation in decisions.
In model (1), the only independent variable is the Selfishness treatment. This variable takes value
1 if the child participated in the Selfishness treatment, and 0 if he participated in the Efficiency
treatment. In model (2), we add age categories. These variables are dummy variables. We interact
each age category with the Selfishness treatment variable. Since the omitted category is the 11 and 14
years old children who participated in the Efficiency treatment, the 7-8 and 9-10 variables measure
the age trends in choosing the egalitarian choice in the Efficiency Treatment. Finally, the interaction
terms between the Selfishness treatment and each age category measure the differences in the
probability of choosing the egalitarian choice between the Selfishness and the Efficiency treatments in
each age category versus the difference in the oldest children. In model (3), we include a female
dummy variable and an interaction term between the treatment and the gender variables. Finally,
model (4) includes all the previous independent variables. Table A displays marginal effects.
TABLE A— ROLE OF CHILDREN'S AGE AND GENDER ON OTHER-REGARDING PREFERENCES
7-8 year olds
(1)
-0.167 ***
(0.056)
-
9-10 year olds
-
7-8 year olds * ST
-
9-10 year olds * ST
-
Female
-
(2)
- 0.017
(0.106)
0.162
(0.117)
0.050
(0.097)
- 0.324**
(0.158)
-0.183
(0.125)
-
Female * ST
-
-
Selfishness treatment (ST)
# observations
Log pseudo-likelihood
Pseudo R2
Wald test statistic
(χ2, p-value)
525
-338.485
0.023
15.6
(<0.01)
525
-333.827
0.036
5.3
(0.26)
(3)
- 0.205**
(0.078)
0.135**
(0.063)
0.069
(0.092)
525
-330.563
0.046
12.35
(<0.01)
(4)
- 0.052
(0.119)
0.159
(0.120)
0.058
(0.095)
- 0.323*
(0.160)
- 0.204*
(0.125)
0.132**
(0.065)
0.069
(0.094)
525
-325.879
0.059
15.87
(<0.05)
Note: ***, **, and * indicate significance at the 1 percent, 5 percent and 10 percent level, respectively.
Model (1) shows that children are less likely to choose the egalitarian option when the
alternative option allows them to increase their own payoff instead of the other’s one. Model (2)
reveals that this effect is mainly due to the youngest children. Indeed, the interaction term 7-8 year
olds*Selfishness treatment measures the difference in the probability of choosing the egalitarian
choice between the Selfishness and the Efficiency treatments in the youngest group versus the
difference in the oldest children: a negative coefficient means that the difference between the
Selfishness treatment and the Efficiency treatment declines with age, i.e. as children become older,
they choose less often the (5-5) option in the Efficiency treatment and more often the (5-5) option in
the Selfishness treatment. Model (3) indicates that girls are significantly more prone than boys to
share tokens equally, independently on the available alternative option. As shown by the
insignificant interaction term between the Selfishness treatment and gender in models (3) and (4),
the impact of children’s gender on the probability to choose the egalitarian option is the same
regardless of the treatment.